This invention relates to a system for controlling the flow of fuel to a prime mover such as a gas turbine engine. More particularly, the invention relates to a system in which the fuel is metered to the prime mover through a valve orifice whose effective area is controlled by a movable valve member such as a flapper valve. In the present system, the flapper valve is adapted to be pivoted by an electrical actuator and is adapted to increase and decrease the effective area of the orifice to vary the rate of fuel flow to the prime mover. The electrical actuator is adapted to be energized by a source of variable voltage whose magnitude is controlled by the throttle setting of the prime mover. The system is designed such that the rate of fuel flow varies substantially as a linear function of the voltage applied to the actuator.
With certain gas turbine engines, there is a requirement that all fuel flow to the engine be cut off for short periods of time when, for example, the compressor of the engine is being used to effect dynamic braking. A pivoted flapper valve, however, is virtually incapable of completely closing off the metering orifice unless very expensive and special manufacturing techniques are used to match the flapper valve with the orifice. Even then, some leakage might occur through the orifice.